The present invention generally relates to a method and apparatus for ophthalmic surgery. More specifically, the present invention is directed to a method and apparatus for controlling fluid flow to and from an eye during ophthalmic surgery.
In retinal and vitreous surgery, a separate needle is used to supply infusion, or irrigation, fluid or suction, for aspiration, respectively.
Phacoemulsification procedures typically include the use of a handpiece for inserting a sleeved needle through a corneal incision and thereafter vibrating the needle in order to emulsify hard nuclear material of the cataract lens. The incision is generally made in the region of the limbus or in the cornea.
An annulus formed between the sleeve and the needle functions as a passage which allows for the introduction, or inflow, of the saline fluid into the eye for irrigation.
The saline fluid prevents the cornea from collapsing as the lens material is emulsified and aspirated. In addition, the saline irrigation fluid aids in the aspiration of emulsified cataract lens material from the eye. The aspiration is conducted through the hollow center of the vibrating needle. The handpiece and needle are connected with an external power source, an irrigation fluid source, and a vacuum source. A control system provides for coordinated ultrasonic vibration, irrigation and aspiration of fluids to and from the eye.
Heretofore, irrigation fluid pressure has been established through the use of an elevated bottle, which provides a source of saline solution. It should be appreciated that fluid control and eye pressure are of utmost importance. Corresponding irrigation and aspiration of flow rates as hereinabove noted are used to maintain the eye in an inflated, pressurized condition during cataract removal. However, the incision size is important since it provides an alternate route for leakage of fluid from the eye.
This leakage causes diminished inflation of the eye during cataract surgery and occurs between the edges of the incision and exterior surfaces of sleeved needle. During the phacoemulsification procedure, the needle is manipulated and such manipulation can lead to wound stretching. This, in turn, changes the leakage rate from the eye and compounds the problem of balanced irrigation and aspiration fluid flow and the maintenance of a proper pressure state of the eye during surgery.
Accordingly, variation in wound construction, sleeve/incision geometry and needle size are important as they relate to fluid leakage from the wound. Deflation of the eye, which may be caused by such leakage, may cause certain tissue within the eye to collapse within one another or on the sleeved needle extending into the eye. In this manner, fluid loss may cause damage to the cornea, iris, or lens capsule which surround the cataract.
One method for counteracting fluid leakages as to increase the amount of irrigation and aspiration fluid flow which is inconveniently done through raising and lowering of the irrigation source bottle along with a concomitant adjustment in aspiration rate.
Accordingly, there is a need for a system for coordinating irrigation fluid flow and aspiration flow during ophthalmology surgery procedures. The present invention fills that need.
A method for controlling fluid flow to and from an eye during ophthalmic surgery includes introducing irrigation fluid into an eye and aspirating fluid from the eye. During fluid flow initial irrigation fluid pressure is determined. Irrigation fluid flow, aspiration fluid flow and maximum vacuum is adjusted based on the determined initial irrigation fluid pressure. Thereafter irrigation fluid pressure is continuously determined and irrigation fluid flow, aspiration fluid flow and maximum vacuum is continuously adjusted based on the continuous determination of irrigation fluid pressure.
A handpiece suitable for use in phacoemulsification procedures while producing the method of the present invention, generally includes an ultrasonically driven, hollow, sleeved needle and the method, in accordance with the present invention, further includes the steps of inserting the needle and sleeve into an eye for phacoemulsification of eye tissue. Irrigation fluid is introduced into the eye through an annulus established between the sleeve and the needle and fluid is aspirated from the eye through the hollow needle.
An initial irrigation fluid pressure is determined and in response thereto irrigation fluid flow and aspiration fluid flow are adjusted in order to initially maintain proper eye pressure within the eye.
Thereafter, irrigation pressure is continuously determined and in response thereto, the irrigation flow and aspiration fluid flow are adjusted based upon the continuous determination of irrigation fluid pressure. Importantly, the method does not include the raising and lowering of a bottle of irrigation fluid as is necessary in prior art methods. The present invention is also distinguished from prior art method in that the fluid flow rates are automatically regulated, or adjusted based upon irrigation fluid pressure determination. This is to be distinguished from current method in which control of irrigation fluid is maintained by feedback from a surgeon based upon visual observation of tissue under the affects of irrigation. In addition, the surgeon control of irrigation is limited to an on/off control valve and adjustment of the irrigation fluid source height.
In the present invention, the introduction of irrigation fluid into an eye is performed through the use of a positive displacement pump and the step of adjusting the irrigation fluid flow includes adjusting the pump speed.
The determination of irrigation fluid pressure many be done through the use of a transducer disposed in a line interconnecting the pump and handpiece or through direct measurement of pressure within the eye.
The adjustment of aspiration fluid flow may include setting a maximum aspiration vacuum pressure as a function of determined irrigation fluid pressure. More particularly, this maximizes aspiration vacuum may be a linear function of the determined irrigation fluid pressure.
The change of irrigation fluid pressure may also be utilized in accordance with the present invention for providing an indication of wound leaking.
The apparatus in accordance with the present invention for controlling fluid flow to and from a phacoemulsification handpiece in order to accommodate changes in incision size and would stretching during eye surgery generally includes a supply of irrigation fluid and a positive displacement pump for introducing irrigation fluid from the supply of irrigation fluid into an eye through an annulus established between a sleeve and a needle of a handpiece.
A vacuum source is provided for aspirating fluid from the eye through the hollow portion of the needle and a pressure sensor is provided for determining pressure of irrigation fluid introduced into the eye.
A control system is provided for adjusting irrigation fluid and the aspiration fluid flow rates in response to the determined irrigation flow pressure. More particularly, the pressure sensor may be disposed in a line interconnecting the positive displacement pump in the needle or a pressure sensor disposed in the eye.
The control system may also include an indication for enabling monitoring by a surgeon of wound construction consistency based upon irrigation of fluid pressure.